Question

I am trying to write a program which read the file and print lines from line#30 to line#50 but not able to achieve it.

main() {

FILE *fp;
char ch;

int nol = 0;
fp = fopen ("test.txt","r");

while (1){
    ch = fgetc(fp);

    if (ch == '\n')
        nol++;


    if (nol > 30 || nol < 50){
        printf ("value of NOL is %d\n", nol);
    }


    if (ch == EOF)
        break;


}
fclose (fp);
printf ("\nNumber of line in file: %d\n", nol);

I tried with if nol >=30 and nol <=50 condition and tried to print but that is not working. Any input will be of great help.

Answer 1

First, the logic part.

Generally we think of line numbers as beginning at 1 instead of 0. So initialise nol to 1.

If you want to display lines 30 to 50, then you need to include them in the test. Use >= instead of > (same for <).

And of course you need to use && instead of ||, otherwise your condition is always true.

If you want to actually display the lines, you need something like this:

if( nol >= 30 && nol <= 50 ) putc(ch);
if (ch == '\n') nol++;

Note the order of the statements.

But really, you should look at using fgets if you want to display the lines, instead of reading one character at a time.